Priming piston reciprocating displacement pumps are well known and have sold for many years by a number of manufacturers such as Graco Inc. (assignee of the instant invention). Such pumps have proven to be less than optimum in the past as restrictions provided by the piston check valve often lead to unbalanced pressures during the up and down strokes of the pump due to the pressure differential which forms across the check valve.
It is therefore an object of this invention to provide a piston check valve which minimizes pressure drop across it and which maximizes flow there through.
It is further an object of this invention to provide a check valve which is easily and inexpensively manufactured.
It is yet a further object of this invention to provide a piston check valve which is high in strength and not subject to fatigue failure.